Measurement of Fineness of Cotton by Air-Flow Methods

Abstract

Using 7 varieties of cotton harvested at different times to give an extremely wide range in fiber development, a study was made of the air-flow method of measuring fineness and maturity of the lint. The data show that when porosity meters are calibrated in units of weight per unit length of fiber (i.e., fineness) the curves for different varieties of cotton are quite different. This is due to the fact that resistance to air-flow through a fiber plug correlates more closely with the surface area of the fibers composing the plug than with their fineness. This surface area varies with variety and maturity, independently of the fineness of the cotton. Using a plug of constant weight and volume made of fibers having a constant density enables the use of a simple theory which predicts essentially the actual variation of air-flow with both variety and maturity of the cottons tested. Two quite different types of air-flow apparatus are shown to give similar results that are more consistent with the specific surface † of the several cottons than with the fineness of the fibers. For several cottons, the air-flow data published by the U. S. Department of Agriculture for the 1948 crop are compared with the previous 10-year averages for fineness which had been measured by counting and weighing the fibers.